The present invention relates to a method for producing osteo-integrating surfaces on skeletal implants (substrates) that are made from metal or metal alloys and to skeletal implants having an osteo-integrating surface.
Skeletal implants require a high strength and resistance but also a good compatibility with the surrounding biological medium or tissue. Metals or metal alloys have been employed as skeletal implant materials for some time. Such skeletal implants, upon insertion into the biological medium, respectively tissue, are known to form a surface oxide layer in that specific medium at random. In the past, skeletal implants made from titanium have been implanted without applying any outer coating, whereby, due to a reaction in the biological medium, a titanium dioxide layer is formed more or less randomly, on the surface of the titanium material. It has also been tried to form a titanium dioxide coating or layer on the titanium skeletal implants by an anodic coating process before the implants are introduced into the biological medium. The titanium dioxide layers resulting from this process usually have a thickness of 4.times.10.sup.-7 m.
However, the randomly formed coatings have proven to be too thin, are porous and easily damaged. The coatings or layers applied by the anodic coating process usually have the same drawbacks. Once an oxide layer has been damaged, the damaged areas lead to friction-induced corrosion and also to the formation of titanium compounds of a low oxidation state. These titanium compounds in general cause necrosis in the surrounding body tissue.
Another problem of the known skeletal implants is that the skeletal implant in general does not bond in the desired manner to the bone it is implanted in. It has been tried to overcome this problem by providing the skeletal implant with a porous surface in order to increase the surface area available for adhesion respectively ingrowth, of the surrounding tissue. However, this measure is not successful in all cases. Also, the adhesion of the implant to the bone lacks sufficient strength. It is therefore an object of the present invention to provide a method for applying oxide layers or coatings onto skeletal implants, whereby these oxide layers, on the one hand, provide excellent integration characteristics into the biological medium, are uniformly applicable and also have a high mechanical resistance, and, on the other hand, also provide good osteo-integrating characteristics. The method should also be easy to perform. A skeletal implant that has excellent integration characteristics into the biological medium, is uniformly applicable and also has a high mechanical resistance, while, at the same time, demonstrates good osteo-integrating characteristics, is provided as well.